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Migrating Disks Between Data Stores

Publication Date:  2014-11-28 Views:  105 Downloads:  0
Issue Description
Customer needs to know the conditions of the disk migrating.
Solution
On the FusionCompute, migrate disks from a data store to another one. The data store-based migration applies to both bound and unbound disks.

The migration scope, migration restrictions, and configuration mode modification for the unbound disks are the same as those of the bound disks in the Stopped state.

Virtualized data stores include network attached storage (NAS) devices, Local Pome, or LUN Pome data stores, and block storage devices include storage area network (SAN) devices and local hard disks.

Migration scope

When the VM is in the Stopped state, the migration can be performed:
• Between virtualized data stores
When the VM is in the Running state, the migration can be performed:
• Between virtualized data stores
• From a block storage device to a virtualized data store

Migration restriction

The following restrictions are proposed during the disk migration:

A Sharing disk that has been attached to a VM and the disk of a linked clone cannot be migrated.
A VM in the Running state does not support the migration of non-persistent disks, disks on a snapshot VM, or disks on an iCache-enabled VM. Therefore, migrate disks after stopping VMs.
A VM in the Stopped state does not support the migration of non-persistent disks or disks on a snapshot VM to a block storage device.

Impact on the System

Do not perform unauthorized maintenance operations, such as hibernating or restarting a VM, during migrating.
Migrating disk may cause disk attributes change.
After a disk affected by snapshots is migrated from a virtualized storage device to a block storage device, the Not affected by snapshot attribute of the disk changes to not affected by snapshots.

- If a disk of the VM in the Running state is migrated, the configuration mode of this disk changes as follows: 



- If a disk of the VM in the Stopped state is migrated, the configuration mode of this disk changes as follows: 



Conditions

You have logged in to the FusionCompute.
The VM carrying the disks to be migrated are in the Running or Stopped state.
The destination data store has sufficient storage space. If the total space of the disks to be migrated is greater than 90% of the free space on the destination data store, the migration will fail.
The source and destination storage devices are associated with the same host.

Procedure

Choose VDC Management > Storage Management.
The Storage Management page is displayed.

In the navigation tree on the left, choose Site name > Data store name.
The Getting Started page is displayed.

In the Operation area on the Summary page, click Disk Migration.
The Disk Migration page is displayed.


Figure 1 Disk Migration



In the disk list on the left, select the disks to be migrated, and click .
The disks are added to the list on the right.

Click Next.

Figure 2 Configure Migration



Select the target data store and set Migration rate.
The value of Migration rate can be:

Medium: The system resource usage is low if this option is selected.
Quick: The system resource usage is high if this option is selected. Therefore, select this value if the service load is light.
No limit: The system does not limit the migration rate.

To change the configuration mode of the destination disk, locate the row that contains the destination disk in the Select destination configuration mode area, click Destination Configuration Mode, and select the desired configuration mode.
This modification applies only to a Common disk of the VM in the Running state.


Common: The system allocates disk space based on the disk capacity. During disk creation in this mode, data remaining on the physical device will be reset to 0. The performance of the disks in this mode is better than that in the other two modes, but the creation duration may be longer than that required in the other modes.
It is recommended that system disks use this configuration mode.

Thin provisioning: In this mode, the system allocates part of the configured disk capacity for the first time, and allocates the rest disk capacity based on the storage usage of the disk until all the configured disk capacity is allocated.
If the data store type is FusionStorage, only this mode is available. If the data store type is Local or SAN, this mode is unavailable.

Thick provisioning lazy zeroed: The system allocates disk spaces based on the disk capacity. However, data remaining on the physical device is zeroed out only on first data write from the VM as required. In this mode, the disk creation speed is faster than that of in the Ordinary mode, and the I/O performance is medium between that of in the Ordinary and Thin provisioning modes.
This mode is supported only when the data store is of the Local Pome or LUN Pome type.


Click Migrate.
A message is displayed, indicating that the VM migration task is submitted successfully.

Click Close.
To cancel a migration task, locate the row that contains the task, click Operation, and select Cancel. Note that an ongoing task cannot be cancelled. Take a batch task for migrating three disks for example. If you cancel this task when disk 1 has been migrated, disk 2 is being migrated, and disk 3 has not started migration, disk 1 will remain in the new data store, disk 2 will continue migration, and only the migration for disk 3 will be cancelled.

If the selected disks have been attached to a VM, some disks cannot be migrated if the ongoing migration task is cancelled. If such a case occurs, the VM can be used as normal, but some disks on the destination data store, such as the memory swap disk, may not be displayed on the system portal. Therefore, when you query information about this data store at this time through the system portal, VM information can be displayed but disk information cannot be displayed. To migrate the invisible disks from this data store to other data stores, you need to migrate all disks on the VM to other data stores first.

END